SOS in Morse Code

SOS in Morse code is ···−−−···: three dots, three dashes, three dots, sent as one unbroken signal. It is the international distress signal, agreed in 1906 and in use since 1908.

SOS

···−−−···

Sent as one run of sound with no gaps between the letters.

How to signal SOS

MethodHow
Flashlight or phone torch3 short flashes, 3 long flashes, 3 short flashes. Pause and repeat.
Whistle or horn3 short blasts, 3 long blasts, 3 short blasts.
Tapping3 quick taps, 3 slow taps, 3 quick taps on a pipe or wall.
Mirror in sunlightFlash the sunlight toward a plane or ship in the same short-long-short rhythm.
On the groundWrite SOS in large letters with stones, logs or in snow so it can be seen from the air.

In a real emergency, always call your local emergency number first if you can (for example 112 in Europe or 911 in the US).

Why is SOS sent without gaps?

Normally there is a pause between letters. SOS is different. It is a "prosign", a special signal sent as one continuous run: ···−−−···. Written as separate letters it would be ··· −−− ···, which still reads as S O S, so both forms are understood.

When did SOS become the distress signal?

Early radio operators used different distress calls. In 1906 the Berlin International Radiotelegraph Convention picked ···−−−··· because it is easy to send and hard to confuse with anything else. It came into force in 1908. One of the most famous early uses was by the Titanic in 1912, whose operators sent both CQD and SOS.

Questions people ask

What is SOS in Morse code?
SOS is ···−−−···: three short signals, three long signals, three short signals. It is sent as one unbroken pattern, without the usual pauses between letters.
What does SOS stand for?
Nothing. SOS was chosen because the pattern is simple and hard to mistake. Phrases like "Save Our Souls" and "Save Our Ship" came later and are not the real origin.
When did SOS become the distress signal?
SOS was agreed at the International Radiotelegraph Convention in Berlin in 1906 and came into use in 1908. Before that, many British radio operators used CQD.
Is SOS still used today?
Ships switched to a satellite-based distress system (GMDSS) in 1999, so Morse SOS is no longer the official sea distress call. But SOS is still widely understood, and signalling it with light, sound or marks on the ground can still attract help.
How do I send SOS with a flashlight?
Three short flashes, three long flashes, three short flashes. Make the long flashes about three times longer than the short ones. Pause, then repeat.

Sources

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